Mijung Noh

Synthesis, Thermal, and Electrochemical Properties of AlPO4-Coated LiNi0.8Co0.1Mn0.1 O 2 Cathode Materials for a Li-Ion Cell

Although LiNi 0.8 Co 0.1 Mn 0.1 O 2 cathode material has a larger specific capacity than LiCoO 2 , their thermal instability has hindered their use in Li-ion cells. An AlPO 4 coating on the LiNi 0.8 Co 0.1 Mn 0.1 O 2 cathode, however, noticeably diminished the violent exothermic reaction of the cathode material with the electrolyte, without sacrificing the specific capacity of the bare LiNi 0.8 Co 0.1 Mn 0.1 O 2 (188 mAh/g at 4.3 V charge cut off). The results were consistent with the thermal abuse tests using Li-ion cells; the AlPO 4 -coated LiNi 0.8 Co 0.1 Mn 0.1 O 2 cathode did not exhibit thermal runaway with smoke and explosion, in contrast to the cell containing the bare cathode. In addition, the AlPO 4 -coated LiNi 0.8 Co 0.1 Mo 0.1 O 2 cathode exhibited a superior cycle-life performance compared to the bare LiNi 0.8 Co 0.1 Mn 0.1 O 2 .

Controlled Nanoparticle Metal Phosphates (Metal = Al , Fe, Ce, and Sr) Coatings on LiCoO2 Cathode Materials

Despite the fact that the same coating concentration and annealing temperature are used for MPO 4 nanoparticle coatings (M = Al, Fe, Ce, and SrH) on a LiCOO 2 cathode, the extent of the coating coverage is influenced by the nanoparticle size or morphology. Nanoparticles (AlPO 4 or FePO 4 ) with a size smaller than 20 nm led to the complete encapsulation of LiCoO 2 , but those with sizes greater than 150 nm (CePO 4 ) or with whisker shapes (SrHPO 4 ) led to partial encapsulation. This difference affected the discharge capacity. The LiCoO 2 completely encapsulated with AlPO 4 or FePO 4 showed the highest discharge capacity of 230 mAh/g at 4.8 and 3 V at a rate of 0.1 C (=18 mA/g), which diminished with decreasing coating coverage in the order of Al ∼ Fe Ce > SrH > Fe > bare cathode. This is consistent with the capacity retention result obtained at 90°C storage for 4 h.

Flexible high-energy Li-ion batteries with fast-charging capability

With the development of flexible mobile devices, flexible Li-ion batteries have naturally received much attention. Previously, all reported flexible components have had shortcomings related to power and energy performance. In this research, in order to overcome these problems while maintaining the flexibility, honeycomb-patterned Cu and Al materials were used as current collectors to achieve maximum adhesion in the electrodes. In addition, to increase the energy and power multishelled LiNi0.75Co0.11Mn0.14O2 particles consisting of nanoscale V2O5 and LixV2O5 coating layers and a LiδNi0.75-zCo0.11Mn0.14VzO2 doping layer were used as the cathode-anode composite (denoted as PNG-AES) consisting of amorphous Si nanoparticles (<20 nm) loaded on expanded graphite (10 wt %) and natural graphite (85 wt %). Li-ion cells with these three elements (cathode, anode, and current collector) exhibited excellent power and energy performance along with stable cycling stability up to 200 cycles in an in situ bending test.